Magnetic switch sensors are widely used in various applications, including consumer electronics, white goods, three common types of utility meters (electricity, water, gas), automotive, and industrial applications, among others. The current mainstream magnetic switch sensors utilize Hall sensors or anisotropic magnetoresistive (AMR) sensors. For utility meters and in consumer electronics, Hall and AMR switch sensors may consume up to a few microamps, but this is obtained at the expense of reduced operating frequency, the operating frequency of ten hertz. Also, the switching point tens of gauss; in environments that require high operating frequencies, such as automotive, industrial applications, the power consumption of AMR and Hall switch sensors is in the mA level, and the operating frequency is on the order of kilohertz.
Magnetic tunnel junctions (MTJ) have recently been incorporated as sensor elements in many industrial applications. These sensor elements are composed of tunneling magnetoresistive multilayers. The electrical resistance of the magnetic multilayer depends on the magnitude and the orientation of the external magnetic field. In the low-power consumption fields, such as the consumer electronics and three-meters, the MTJ sensors are operating at the frequency of a dozen Hz with the switch point at tens of gauss. In the automobile and other industrial fields under the high frequency condition, the MTJ sensors are consuming only the power of uA at the MHz level.
The power consumption for the existing switch sensors are high in terms of sleep or state power, and low in terms of operating frequency. It requires a switch sensor with a high sensitivity, an excellent response to high frequency and a small volume in hibernation or work status of low power consumption